The invention comprises robotic equipment for carrying out operations in pipelines which can be applied to the activities of the production and transport of petroleum and its derivatives. More specifically, it relates to a vehicle capable of introducing tools, equipment or materials within pipelines, especially when long and installed under conditions of difficult access, for the purposes of removing obstructions, making inspections, repairs and other work. Although designed for use in the work of the production of petroleum and derivatives, the invention can be applied to any other industrial areas which make use of pipelines, or other confined spaces which may need work to be done within them, such as for example systems for the distribution of water, gas, basic drainage, hospital systems, air ducts, etc., energy generating plants, refineries, plants involving classified industrial processes (nuclear plants, etc.), plants for miscellaneous industrial processes, etc.
With the development of new technologies, the offshore production of petroleum is becoming viable at increasingly greater depths. This scenario involves the need to install an extensive system of pipelines at considerable depths. Together with other technological challenges which are being overcome, mainly those relating to the increasingly exacting specifications for equipment because of the high pressures, it is common for problems of various kinds which have not always been foreseen in advance to occur. Of these, mention may be made, for example, of problems brought about by low temperatures, which are normally associated with the properties of the fluid transported.
In the case of the problems arising as a result of low temperatures, there has been observed a tendency for reduction in the fluidity of oil, the formation of hydrates, the deposition of paraffin and, frequently, the occurrence of severe restrictions in flow or even blockages in pipelines. Clogging, which can also be caused by the deposition of sand or other materials, sometimes occurs at long distances from the nearest access points. In this way it is difficult or even impossible using the technology currently available to bring tools, equipment or other materials up to them. In work within pipelines, whether submarine or not, a prior survey of the conditions of the system is to be recommended, including at least:
survey of the layout of the pipelines to detect any differences between design and construction,
determination of the type of protection present in the pipeline (mechanical, chemical, cathodic, etc.),
investigation of the historical record of operational problems (occurrences), age of the installation, length and conditions of use, etc.,
an examination of routine inspection reports, among other technical documents.
One of the most important factors which has to be considered is the dimensional factor. Nominal diameter, bends, connections, branches, ovalization, dents, imperfections in the pipeline wall, etc., will interfere directly with the choice and performance of the system used to carry out work. Recently, much has been invested in the development of multidimensional pigs and techniques based on collapsing the pipelines, with a view to dealing with the dimensional aspects mentioned above which very often literally consist of accidents along the route. Some of these aspects, like bends and branches, may be known from the design and/or field surveys. It is common for pipelines to have sharp bends, and these significantly restrict the means available for work. At the present time the API standards accept a minimum radius of curvature of three times the nominal diameter for a particular gauge. Where the interruption in flow is total, the so-called hydraulic xe2x80x9cwedgexe2x80x9d is needed, which makes it impossible to use the main tool available for clearing long pipelines, which is a pig. Use of the latter equipment presupposes the existence of flow and a pressure difference within the pipeline. If a submarine pipeline breaks, the fluid tends to flow out into the external environment until a situation of pressure equilibrium is obtained. In this situation the pipeline has high operational instability as its main characteristic. Any attempt at action which involves a change in pressure will disrupt this precarious equilibrium and cause more spillage. The need to empty the pipeline, so that the causes of the accident can be investigated more closely and better known, must without fail go through a set of safety measures. At the present time, for fluid to be withdrawn from within the pipeline, it is necessary to use pumping, and this makes drainage unavoidable. As a protective measure temporary pipes are fitted and tested for leaks.
In both the situation where flow is totally obstructed and in the situation where pipelines are broken it is desirable that equipment should be developed which is capable of carrying some equipment inside the pipeline to the site of the problem without the need for a pressure difference. In the case of a broken pipeline, for example, the possibility of reaching the region of the failure from within the pipe with something which has yet to be developed which would make it possible to seal it and make use of the pumping pressure acting in a favourable direction, outwards from the interior, making the sealing means adhere even more, would constitute an innovative method for dealing with this type of problem. This accessory is already under development as one of the items which might carry out emergency repairs. This invention is designed to overcome problems such as those mentioned above, among others. It may act as a tool carrier, travelling within a pipeline, within specific diameter ranges, and having bends within the normal limits. It may also be used for surveying the profile of the internal surface of a pipeline, acting as a gauge. To sum up, the invention may be used for inspections and various types of work at points which are inaccessible for the means available at this time. Its movement within pipelines, in both directions, is based on the control of friction and on the use of non-reversing wheels mounted on towers capable of rotating about their vertical axis under remote control.
At the present time, equipment known as a pig is used for the work of removing encrustations in pipelines for the transport of petroleum. This comprises an object of round or oval shape, generally manufactured from some polymer, which moves along a length of the pipeline. While travelling, the pig scrapes off encrustations from the internal surface of the pipeline which partly obstruct it. The launcher is installed at the start point and the so-called pig-catcher is installed at the other end.
However, in order to move, the pig requires a pressure difference between the two ends of the length of the pipeline and the presence of a flow of fluid. When there is total obstruction of the pipeline there is no pressure difference, the fluid does not circulate, and a form of hydraulic plug is formed, and as a consequence pigs cannot be used. When there is a total blockage of flow a possible alternative to a pig is a flexitube. This is a flexible tube which has some strength and is provided with means for being passed inside the pipeline, which is used for various types of work. However, the scope of this equipment is limited. If the blockage point is at a distance, it may not even be possible to reach it. Although having considerable strength, the flexitube has limited capacity for application of the force which it requires in order to be pushed into the pipeline without suffering bending or excessive deformation. Mainly because of friction, there is a tendency for the flexitube to form a helicoid supported against the internal surface of the pipeline. As the flexitube moves forward, friction increases considerably, and more and more force is needed to push it into the pipeline. Formation of the helicoid and a consequent spring effect is thus accentuated. Beyond a certain point this prevents the front of the flexitube from advancing, because of the limitations of the material of the flexitube itself or the equipment pushing it, limiting the scope of its action. At the present time it is possible to reach a distance of the order of one and a half kilometres using this type of equipment. Thus, if the location of the obstruction is at a greater distance, which is quite common in an extensive pipeline system, the flexitube cannot be used. As part of the programme of technological development known as Deepstar, the Radoil Tool Co., in association with Ambar Production Services, has developed a type of pulling mechanism, together with small trucks, for use with flexitubes in order to assist their movement within pipelines. It has, however, been found that the scope of this system is limited and that it needs further development to meet the operational needs resulting from maintenance work in an extensive system of pipelines.
Another alternative, when the flow is totally blocked, is the equipment known commercially as the Well Tractor, manufactured by the company Welltec. This equipment is able to move within pipelines and can be used for particular types of work. However, the Well Tractor was designed for use in wells, and its excessive length and limited scope make it unsuitable for some types of routes and distances frequently found in petroleum pipeline systems. Brazilian application PI 9904364-5, Remote-Controlled Vehicle for Work within Pipelines, of Sep. 28, 1999, by the Applicant, relates to equipment having the ability to move within pipelines, which can be used in cases of complete obstruction occurring at great distances from the access point, and for other types of operational problems, needs or emergencies. The great advantage of this equipment over a conventional pig, in terms of design, is that it is possible to transport tools to the requisite region independently of any flow. The equipment is unaffected by a natural hydraulic block brought about by total blockage of the pipeline. However, the vehicle to which application PI 9904364-5 relates was not developed for operations in pipelines with sharp bends. A pipeline system normally incorporates bends of up to three times the nominal diameter of the pipe, which acts as an impediment to the full use of this equipment.
To overcome this problem, this invention provides an improved design of this type of equipment, which comprises two identical modules symmetrically coupled by means of a type of joint which makes it better able to take up marked misalignments in route. Another advantage of the design of the equipment according to this invention is simplification of the traction system which is responsible for movement of the assembly along the pipeline. Comparing this invention with the vehicle to which application PI 9904364-5 relates, it will be seen that the latter comprises a single block and that the set of supporting fins therein has been improved and has changed from three sets of three fins to two sets of two wheels. These differences offer different applications for the invention in comparison with PI 9904364-5. It is indicated for pipelines having bends up to the maximum limit in the standards and preferably for light loads. The vehicle to which PI 9904364-5 relates is on the contrary indicated for heavier loads and for predominantly straight pipelines, or with only long-radius bends or small misalignments. Acting as a tool carrier, the invention can position, move, fit or operate, jointly with other equipment, for example:
non-destructive inspection and testing systems such as ultrasound or X-ray heads,
chemical jetting systems,
nitrogen generation systems (NGS),
image capture and transfer systems,
signalling systems (audible, magnetic, etc.),
systems for surveying the profile of the internal surface of a pipeline.
Another feature of the invention, which operationally is very attractive, is its ability to move in two directions: in an upstream direction and in a downstream direction. The system for reversing the direction of movement, which takes place under remote control, is mounted on board the equipment and can be provided in various ways. In the preferred embodiment described herein the direction of movement is reversed by rotating the tower supporting the wheels by one hundred and eighty degrees about its vertical axis. As a result of this rotation, the non-reversing direction of these wheels is reversed. Rotation of the supporting tower is brought about, in the embodiment in this description, by means of a system of suitably positioned and dimensioned lever arms which are hydraulically activated. There are other possibilities such as, for example, the use of an electrical activator. Replacement of the fins by wheels with a non-reversing system solves the problem of wear on the fins supporting the vehicle to which application PI 9904364-5 relates, which are constantly in contact with the wall of the pipeline when in use. In this invention this contact is made through the wheels. When subjected to stress as a result of friction on the internal surface of the wall, the non-reversing system behaves in two ways:
in one direction it rotates freely, permitting movement of the corresponding module,
in the other it brakes, causing the module to be anchored.
The wheels may be provided with additional devices such as, for example, position detectors and odometers, so that as it moves along the pipeline the equipment automatically produces a profile of the internal surface of the pipeline at a remote console. The equipment according to the invention may be fitted with accessories and the means necessary for operations and the transport of various materials, devices and equipment. Mention must be made of the possibility of carrying out difficult and complex fishing operations, which are so frequent in the work of petroleum production. The rescue of items which have fallen into confined spaces, with continuous monitoring, may also be considered.
This relates to robotic equipment having the ability to move and carry out various operations, drawing along an umbilical and carrying accessories, tools or materials within a pipeline or other confined space, which are preferably cylindrical. It comprises two identical modules joined by a flexible joint which connects the shafts of hydraulic piston systems propelling the modules. Each module basically comprises a main hydraulic piston system which is responsible for movement of the module, a positioning tower on which two wheels, provided with a non-reversing system, are fitted in symmetrical positions in relation to the longitudinal axis of the equipment and means, for example two hydraulic piston systems, for rotating the positioning tower through one hundred and eighty degrees about its vertical axis. As a result of this rotation, the direction of movement of the equipment in the pipeline or confined volume is reversed. Although hydraulic equipment has been described, other forms of power may be provided, both for movement of the equipment and for rotation of the wheel positioning towers. An umbilical is generally connected to the back of the rear module. Through the development or coupling of interfaces the invention makes it possible to position tools, equipment or materials at a remote point within a pipeline having bends within the limits of the standards, in order to clear obstructions, perform inspections or other operations.